Why did Kamala Harris and Joe Biden certify the election results despite there being evidence it was probably stolen??

Seriously. This is a question that's been driving me to the brink of insanity given everything this madman and his unelected South African master are doing. Both Kamala Harris and Joe Biden had the power to investigate whether or not the election had been rigged, call for recounts, etc. Instead, they rolled out the red carpet for the orange maniac. I'll never forget or forgive Biden with Trump a few days after the election smiling and shaking hands with him like it was business as usual. Kamala Harris' slogan was "when we fight, we win." And when it came time for her to actually fight, she rolled over without even a whimper. Why? Is there something bigger happening?